textproduct: Rapid City

KEY MESSAGES

-Cloudy and cool Friday with fog possible on the SD Plains

-Mild and dry most of this weekend

-Unsettled and cooler to start next week with a good chance of rain Sunday night into Tuesday, some high elevation snow is possible as well

UPDATE

Issued at 941 PM MDT Thu Oct 29 2026

Latest nighttime microphysics RGB showed two areas of stratus. One over NE which is heading north toward the CWA. Another over central ND, which will expand southwest into the Black Hills foothills as T/Td spreads converge overnight. This will lead to patchy/areas of fog primarily on the SD plains. Previous forecast had things well depicted. Made some minor updates for the latest timing/coverage. Did lower MaxT for Friday where stratus is not expected to scatter. Perennially insightful NAM guidance has a high of 43F for KRAP Friday. NBM guidance 5-10F higher, so didn't go wild with lower temperatures. Something to be aware of, however.

DISCUSSION

(This Afternoon Through Wednesday) Issued at 1141 AM MDT Thu Oct 29 2026

Deep upper trough over the PAC NW and western Canada will support general SW flow into the weekend. Departing impulse giving way to clear skies today as winds shift easterly behind the sfc reflection. Expect highs in the 50s and 60s. Southerly flow will develop tonight and support a push of low level moisture into the region. This will support low clouds and areas of fog over most of the SD Plains. Temps will struggle to rise Friday on the SD Plains with 40s and 50s expected for highs. With clear skies and better mixing, expect 60s over northeast WY. There is a low chance for a few showers Friday night toward central SD as a disturbance skirts the region to the south and forces pos theta-e adv in the Northern Plains. Low clouds and fog are likely to stick around on the SD Plains as southerly flow persists Friday night. Winds will veer in the low levels Sat and allow mix out of low clouds and fog as drier are mix in. However, mid and upper level clouds look to increase which could hold temps down a bit. Western CONUS upper trough will lift out of the western Pac early next week, with broad lift spreading into the region starting Sunday night. Ample low level moisture will advect ahead of this system which will allow for a decent chance of precip on the SD Plains, esp toward central SD. The best chance for precip will be Monday when the main trough passes over the region. Very warm system for early Nov, with mainly rain expected. However, enough cold air may entrain into the back of the system Monday to allow for some higher elevation snow across northeast WY and the Black Hills. This could some support some light snow accums there, esp in the northern Black Hills. Things will dry out west to east Tues with cooler conds expected for the rest of the week as NW flow becomes established.

AVIATION

(For the 06Z TAFS Through 06Z Friday Night) Issued At 1043 PM MDT Thu Oct 29 2026

Low stratus and MVFR/IFR ceilings will overspread portions of the western South Dakota plains and the Black Hills foothills after 06-08z. Fog will also develop (below 1SM in some areas) after 07-09z tonight. While some improvement in visibility is expected through the day tomorrow, low ceilings will persist through the forecast period. Conditions will generally remain VFR across northeastern WY.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.